Hot workability characteristics of as-cast titanium alloy Ti-6Al-2Zr-1Mo-1V: A study using processing map

The intrinsic workability of as-cast Ti-6Al-2Zr-1Mo-1V alloy was investigated by using processing maps constructed from the stress-strain data generated by isothermal compression tests with a height reduction of 60% over a range of temperatures 1073-1323 K and strain rates 0.01-10 s(-1). As the true strain was 0.3, 0.5, 0.7, and 0.9, respectively, the responses of strain rate sensitivity (m-value), power dissipation efficiency (eta-value) and instability parameter (xi-value) to temperature and strain rate were evaluated. By the superimposition of power dissipation and instability maps, the stable and unstable regions were clarified clearly. In further, in the stable area the regions have the highest efficiency of power dissipation (>= 0.2) were identified and recommended. On the basis of determination for domains with dynamic recrystallization (DRX) microstructural evolution, the full DRX regions were identified in the processing map at true strain 0.3-0.9. Then not only the domains optimized were validated by DRX refined microstructures, but also the regimes of flow instabilities were validated by the microstructures involving wedge cracking and deformation twinning. The optimal working parameters identified by processing maps and validated by microstructure observations contribute to designing the reasonable hot forming process of Ti-6Al-2Zr-1Mo-1V alloy without resorting to expensive and time-consuming trial-and-error methods. (c) 2012 Elsevier B.V. All rights reserved.